I can just imagine how poorly it would have worked out if the Packers would have went from a 4-3 to 3-4, when Reggie White was playing DE. He had the moves, and enough speed to work off the line, but wasn't fast enough to play OLB.
If we had 1996 Reggie (or even better, Prime Eagles Reggie) on this roster, we would run a 4-3 hybrid scheme so fast your head would spin. That said, it wouldn't look much different from that Super Bowl year. Fritz ran a hybrid scheme with Sean Jones being a somewhat undersized speed rusher opposite Reggie. And Reggie's good, but not great speed that meant he wasn't the best outside-container player was dealt with by have the SOLB (I can't remember, I think that was Cox back then?) mug the tight end worry about contain in the running game.
Sure, in base, we'd be a 4-3 hybrid. All that really means is that we'd be in a shade (4-3 under) look and the strong (almost always defensive left) outside linebacker would be more of a coverage player. Preston honestly wouldn't be horrible in that role, but he'd be over paid.
In nickel, Reggie (or for a non-Zombie approach) or JJ Watt would give you flexibility. Depending on down and distance, Reggie could either be a 3T defensive tackle or an edge player. In Dime, he'd all but certainly be a DT.